Modern double hung windows are provided with pivot means along the central portion thereof so that the window can be pivoted or tilted along the axis of the pivots out of the plane of the casing to open the windows for ease of cleaning. In order to maintain the windows in place in their normal mode of operation, sliding latches are normally provided which, when engaged, maintain the windows in the same general plane as the window casing. However, these conventional constructions lack sufficient security.
More recently, a window latch for this type of window has appeared which has a locking means similar to that of Gibson U.S. Pat. No. 4,475,311. However, this type of construction has a rotatable locking element which has an upper end in the form of a screw head and a lower end having a bar eccentrically mounted thereon. When a screwdriver is inserted into the screw head and rotated, the bar may be aligned either adjacent the interior end of the latch thereby preventing the latch from being displaced (i.e. a locking mode), or it may be turned 180.degree. to the unlocking mode so that the bar does not interfere with the movement of the latch. This construction requires the use of a screwdriver to lock and unlock, and is therefore difficult and inconvenient to use. The overall construction of this device does not suggest a way to avoid the use of a screw head, while still maintaining a latch construction which is otherwise satisfactory.
Many general purpose lockable latches exist. Among these is the 1859 U.S. Pat. No. 26,518 in the name of Page for a slidable door bolt; U.S. Pat. No. 1,689,101 to Beck which shows a fastening mechanism for a grave vault; and U.S. Pat. No. 742,881 in the name of Little directed to a metallic door bolt, catch and locking button including a spring-actuated sliding bolt. However, these devices are archaic in construction, in some cases being unduly complex, and are unsuitable for use in the present environment.